Overview.
Pulmonary candidiasis is an acute, subacute, or chronic bronchial and pulmonary infection caused by Candida spp. It is more common among fungal infections of the lungs and is mostly nosocomial. Candida infections have been reported to account for 79% of fungal infections, with a particularly high incidence in intensive care units, burn and oncology units.
Etiology
To date, more than 270 species of Candida have been identified, among which the main Candida causing human pathogenicity are Candida albicans, Candida tropicalis, Candida pseudotropicalis, Candida near smooth, Candida kruegeri, Candida stellate, Candida smooth, and Candida gori, all of which are conditionally pathogenic, among which Candida albicans has the strongest virulence and is also the most common. The pathogenicity of Candida is related to the morphology and adhesion ability of the organism, yeast type is generally non-pathogenic, mycelial type is pathogenic. Candida with strong adhesion is also highly pathogenic. Some Candida can secrete toxins and hydrolytic enzymes, destroying tissues.
Normal human skin, oral cavity, gastrointestinal tract, etc. are Candida parasites, under normal circumstances do not cause disease, when the body’s immune defense function declines, parasitized in the oral cavity, the upper respiratory tract of Candida can invade the respiratory tract to cause endogenous infection. Dietary impurity, hospital cross-infection can cause exogenous infection. Indwelling catheters, mucosal ulcers and other disruptions of mucosal integrity can also allow Candida to invade the body. The lungs can be a primary infection or part of a blood-borne disseminated Candida.
Symptoms
1. Bronchitis type
Mild symptoms, cough, cough a small amount of white mucous sputum or pus sputum; examination of the oral cavity, pharynx and bronchial mucosa can be seen covered with scattered punctate white film. Occasionally, dry rales can be heard in both lungs.
2. Pneumonia
Acute pneumonia or sepsis, chills, fever, cough, white mucus sputum or pus sputum with blood, even hemoptysis, dyspnea, etc. The general condition is poor, and dry and wet rales can be heard in the lungs.
3. Allergic type
Difficulty in breathing, itchy nose, runny nose, sneezing, etc. Rales can be heard in both lungs.
Examination
1. Pathogenetic examination
(1) Pharyngeal swab, sputum, bronchoalveolar lavage fluid, pleural effusion, blood and so on, direct smear microscopic examination or Gram stain, Iemsa stain or PAS staining, the specimen found in the bacillus spores and pseudohyphae and mycelium have diagnostic value.
(2) Because normal people can carry bacteria in the throat, sputum culture is positive for more than 3 times to have certain diagnostic significance.
(3) Sampling and culture via fiberscope protective brush (PSB) is more reliable. Due to the short duration of bacteremia, the positive rate of blood culture is low.
2. Histopathologic examination
Fiberoptic bronchoscopy biopsy or percutaneous lung biopsy, histopathological examination of Candida mycelium invasion evidence can determine the diagnosis.
3. Immunologic examination
Immunological detection of anti-Candida antibody, sensitivity and specificity are not ideal, and false negatives are often seen in severely ill patients and immunodeficient patients. Detection of Candida antigens are mainly mannan antigen, 47KD antigen, heat unstable antigen, but there are common antigens between different species of Candida, and some protein components in human serum have similar antigenic determinants with Candida antigens, which need to further improve the sensitivity and specificity.
4.Imaging examination
Chest X-ray of bronchopneumonia type shows deepening of the texture of both lungs, and diffuse speckled and small patchy shadows in the middle and lower lung fields of both lungs. Pneumonia X-ray shows flaky or nodular infiltration, which may spread to the whole lung lobe, and there may be enlarged hilar or mediastinal lymph nodes, or pulmonary edema, and the shadows may change greatly in a short period of time. Hematogenous mostly shows multiple indistinctly bordered granular nodular shadows, and with the progression of the disease, the granular lesions may merge into small nodules of varying sizes.
Diagnosis
The diagnosis can be confirmed by direct smear or culture of Candida in lower respiratory secretions, lung tissue, pleural fluid, blood, urine or cerebrospinal fluid taken by cricothyroid puncture suction or by fibrinoscopy through anti-pollution brushes. A direct smear or culture of sputum for Candida is not diagnostic of fungal disease, as Candida albicans can be found in the sputum of 10% to 20% of normal individuals. If there is 3% hydrogen peroxide gargle 3 times, sputum coughed up from the deeper part of the sputum for three consecutive cultures of the same strain of Candida, then there is a diagnostic reference value.
Differential diagnosis
1. Bacterial pneumonia
Bacterial pneumonia is characterized by high fever, cough, sputum, chest pain, shortness of breath and other symptoms, solid signs and wet rales in the lungs, elevated white blood cell count, and flocculent infiltration shadows on chest radiographs. However, pathogenic diagnosis is more difficult, and the causative organisms need to be isolated from the sputum or pleural fluid.
2. Viral pneumonia
Viral pneumonia usually causes upper respiratory tract infection first, and then spreads downward to cause lung inflammation. Bacterial infection is often induced due to the impaired defense function of the respiratory mucosa. Diagnosis should be based on pharyngeal swab, sputum virus isolation and serum specific antibody measurement.
3. Tuberculosis
There are symptoms such as low-grade fever, night sweats, etc. In the early stage, there is irritating dry cough, and then there is sputum, after the formation of cavity, the cough worsens, the amount of sputum increases, and half of the patients may have hemoptysis. Diagnosis is mainly based on chest X-ray and sputum or other specimens of tuberculosis bacilli or tuberculosis-specific pathologic changes.
4. Other
It also needs to be differentiated from pneumonia caused by pulmonary aspergillosis and Pneumocystis carinii pneumonia.
Treatment
Firstly, treat the primary disease and remove the triggering factors, such as stopping the use of antibiotics, hormones and immunosuppressants. Strengthen the supportive therapy to enhance the immune function.
1. Principles of treatment
(1) Treat the primary disease and remove the triggering factors.
(2) Strengthen supportive therapy.
(3) Application of antifungal drugs: selective use of ampicillin B (AmB), 5-fluorocytosine (5-Fc) and ketoconazole.
2. Principles of medication
(1) Mild cases are given vitamin supplementation, especially vitamin B and C. Or, while stopping broad-spectrum antibiotics and corticosteroids, oral or nebulized inhalation of antifungal drugs is used.
(2) In severe cases, intravenous drug administration is the mainstay, which can be combined with one or two antifungal drugs, and supportive therapy is strengthened.
(3) Stubborn cases can be immunotherapy, such as mycobacterial vaccine injection and other comprehensive treatment.